1. Field of the Invention
The invention relates to an adhesive system for a laminated ophthalmic lens and the related method for applying such an adhesive system between a film and an ophthalmic lens.
2. The Prior Art
Ophthalmic lenses can be tinted or otherwise modified to alter the transmission properties of the base lens. Some dyes can be incorporated into the base material before or after the lens shaping process. Other processes are applied after the lens is formed. One such process involves laminating a film on to a lens surface. These films are often referred to as functional films, which mean that they alter an optical or transmission property in some respect. Polarized films are desirable because they reduce glare without unduly limiting transmission.
There are many ways to make polarized lenses, such as by injecting a lens against a polarized film, casting a lens adjacent a polarized film or laminating the film with a glue, etc. Some prior art methods describe gluing a film by using thermal or UV curable glue or using hot melt adhesives (HMA) or using pressure sensitive adhesive (PSA). However, all these prior art methods have either optical or mechanical performance issue due to unevenness in the glue layer or lack of good adhesion. The adhesion issue is even more problematic in connection either with certain materials used to make organic lenses, or certain materials used to make films.
Therefore, the object of this invention is to provide a very even adhesive layer between lens and the film, independently of the materials used to make the lens and/or the film. This adhesive layer is pre-coated by spin method to get an even thickness on both lens and the film side.
Another object of this invention is to provide the strongest adhesion between a polarized film, such as TAC/PVA/TAC film and a plastic lens, such as epi-sulfur lens material. The new adhesive system can be used on any lens materials, since the last layer of latex could bond to any lens substrates by spin or dip applications.
Another object of this invention is to provide the flexibility of putting an HMA layer either on the lens or on the film depending on the process. With many different types of spin equipment, it will be easier to put an HMA layer on a lens surface rather than a film surface.